Stephen Baxter's new novel Proxima includes a sentient solar sail, but this unique type of spacecraft has a long history in science fiction — and an even longer one in science. Though the idea is 400 years old, it might still become the kind of vessel that we eventually ride to the stars. »3/13/14 9:00am 3/13/14 9:00am

Solar sails are all about "propellantless" propulsion — using photons from the Sun (as opposed to an onboard fuel supply) to push a spacecraft through space. Building on the lessons learned from smaller solar sail missions, like NASA's NanoSail-D and JAXA's IKAROS, NASA is gearing up to to launch the biggest solar… »2/01/13 10:40am 2/01/13 10:40am